The surface proteins of the pulmonary endothelial cell are responsible for the metabolic activities which colllectively are known as the metabolic functions of the lung. The endothelium also participates in the inflammatory response. Changes in surface function during injury suggest a modulation of surface proteins. I hypothesize that endothelia respond to injury with shifts in function which are programmed to initiate and amplify inflammation. These changes in function will be reflected in the selective loss of surface proteins and the expression of new surface proteins. It is the purpose of this research to study the modulation of endothelial surface proteins in injury by examining these proteins in endothelia grown under different conditions. In phase I of this proposal I will 1) develop a highly differentiated model of the pulmonary microvascular endothelium applying existing expertise, 2) examine the surface membrane proteins of aortic, pulmonary arteriolar, venular, and capillary endothelia grown in culture and for comparison the proteins of aortic endothelia harvested but not cultured, 3) look for changes in surface proteins of endothelia during injury in an hyperoxic environment, 4) and develop antibodies (monoclonal and polyclonal) to proteins which are either lost or induced in injury. In phase II of this proposal, information concerning the time course of protein shifts and the immunoreagents developed from phase I will be applied to the study of microvascular injury in a chronically instrumented sheep model of hyperoxic lung injury. These studies will lead to a better understanding of the endothelium's role in the evolution of microvascular injury and will eventually allow me to search for the appearance of proteins in the plasma of critically ill patients which may serve as early indicators of acute lung injury.